Cerebral artery vasospasm is a life-threatening condition triggered by bleeding aneurysms that can cause severe neurological damage. The number of patients suffering from cerebral vasospasm is in excess of 20,000, and the condition often produces permanently crippling effects or death in the 30-40 year old age group that exhibits the highest incidence. The condition responds poorly to drugs and is difficult to treat with balloon angioplasty. On Phase I, we developed a pulsed-holmium-laser-driven catheter which emitted fluid waves that reliably and permanently relieved hemorrhage-induced spasm in canine brain arteries. During Phase ll, we will first verify the exact procedure and hardware to be used in patients, then conduct the first clinical trial of this approach in patients with papaverine-resistant cerebral artery vasospasm. A life-saving treatment for vasospasm will result directly from this work. PROPOSED COMMERCIAL APPLICATIONS At present, there is no permanent treatment for severe cerebral artery vasospasm. Approximately 10,000 healthy, young adults suffer permanent brain damage due to cerebral vasospasm each year, and the development of a permanent laser-based treatment would significantly reduce the number of patients disabled by this condition.